BCG reaction in twin newborns: effect of zygosity and chorionicity.

OBJECTIVE To study local response to BCG vaccination in twin babies and find out the effect of zygosity andchorionicity on BCG uptake. DESIGN Analytical observational study. SETTING Tertiary hospital. METHODS Twin pairs born in the hospital were evaluated for zygosity and chorionicity. BCG vaccination was given within 48 hours of birth to babies >/=33 weeks of gestation and birth weight >/= 1500 g. Follow-up was done at 6,10 and 14 weeks. Local response to BCG vaccination was recorded in the form of no reaction, abortive reaction, papule, pustule, ulcer, scab or scar. RESULTS One hundred thirty three twin pairs were delivered (16 monochorionic, 117 dichorionic); of which zygosity was determined in 110 pairs (81 dizygotic, 29 monozygotic). Two hundred four twin babies qualified for BCG vaccination. After 14 weeks, local reaction was seen in 84.3% babies and scar formed in 41.2% cases. Five abortive reactors and 20 'true non-reactors' were also found. Intra-pair agreement for local BCG reaction was highly significant in both monozygotic/dizygotic, as well as monochorionic/dichorionic twins (P<0.01). However, monozygotic and monochorionic intrapair agreements were not significantly larger than the dizygotic and dichorionic intrapair agreements(P >/= 0.05), respectively. CONCLUSION Local response to BCG vaccination in twin newborn babies follows same pattern as singletons and there is no effect of zygosity or chorionicity on the uptake.